1. Field of the Invention
This invention generally relates to semiconductor device fabrication and more particularly to systems and robots used in wafer processing.
2. Description of the Related Art
Specialized wafer processing systems are used to process semiconductor wafers into electronic devices. In certain of these systems, a carrier containing wafers is loaded into a loading station and transferred to a load lock. Subsequently, a robot picks up a wafer from the carrier and moves the wafer into a reactor (also known as a process chamber). The wafer is processed in the reactor according to a recipe. In a chemical vapor deposition reactor, for example, a thin film of a dielectric material is deposited onto the wafer typically to isolate one layer of the wafer from an overlying layer. Once the film is deposited, the robot picks up and transfers the wafer back to the carrier in the load lock. The carrier is then moved out of the load lock and back into the loading station.
U.S. Pat. No. 5,882,165 to Maydan et al. (xe2x80x9cMaydanxe2x80x9d) discloses a wafer processing system wherein the reactors and other modules of the system are horizontally integrated (i.e. the modules are spread out horizontally). A disadvantage of a horizontally integrated system is that the total floor space area occupied by the wafer processing system increases as more modules, such as reactors and cooling stations, are added to the system. Because floor space in semiconductor fabrication clean-rooms and equipment areas is typically scarce and costly, it is highly desirable to have a wafer processing system which occupies minimal floor space. Further, some components of a horizontally integrated system (e.g. pumps) typically require installation in a remote location because of floor space constraints. A compact wafer processing system is desirable because such a system can be moved, installed, and operated as a single unit in a small contiguous area, thereby obviating the need for complex connections to remotely installed components.
In typical wafer processing systems, robots are employed to automate the movement of wafers between modules. An example of a commercially available wafer processing robot is the SHR3000 robot (xe2x80x9cSHR3000 robotxe2x80x9d) from the JEL Corporation of Hiroshima, Japan (telephone no. 81-849-62-6590). The SHR3000 robot can rotate 340xc2x0, has 200 mm of vertical motion, and can extend its arms 390 mm in the horizontal plane. The SHR3000 , like typical wafer processing robots, cannot readily access a newly processed wafer from a very hot reactor without spending additional time waiting for the reactor to cool down. This is a concern specially in high temperature wafer processing applications such as rapid thermal processing (xe2x80x9cRTPxe2x80x9d) wherein the reactor can reach temperatures of 1200xc2x0 C. Further, the SHR3000 robot""s 200 mm of vertical motion is not optimum for accessing vertically mounted modules. It is desirable to have a wafer processing robot that can withstand high temperatures and can access vertically mounted modules of varying heights.
The present invention relates to a wafer processing system which occupies minimal floor space. In one embodiment of the invention, multiple reactors are vertically mounted (i.e. vertically integrated) to save floor space. The invention also uses vertically mounted load locks and cooling stations. Further savings in floor space are achieved by using a loading station which employs rotational motion to move a wafer carrier into a load lock.
The invention also includes a robot for moving a semiconductor wafer within the wafer processing system. The robot not only extends in the horizontal plane and rotates, but also has a range of vertical motion which allows the robot to access vertically mounted reactors, load locks, cooling stations, and other modules. The robot is internally cooled and supports a wafer using a heat resistant end-effector (i.e. xe2x80x9cfingersxe2x80x9d for lifting a wafer), making the robot compatible with high-temperature semiconductor manufacturing processes.
Other uses, advantages, and variations of the present invention will be apparent to one of ordinary skill in the art upon reading this disclosure and accompanying drawings.